Process of extracting light mineral oil distillates with sulphur dioxide



Patented Feb. 23, 1937 UNITED STATES PATENT OFFICE PROCESS OF OIL DISTILLATES OXIDE Ernest W. Thiele and Fred cage, 111., assignors to Standard EXTRACTING LIGHT MINERAL WITH SULPHUR DI- W. Scheineman, Chi- Oil Company,

7 Claims.

This invention relates to the process of extracting light mineral oil distillates with sulphur dioxide, and it pertains more particularly to the extraction of light petroleum distillates such as petroleum naphthas and cracked naphtha containing anti-detonating constituents with sulphur dioxide for the purpose of separating the anti-detonating portion of the naphtha from the remainder thereof which is called the raflinate.

The object of our invention is to provide a novel and efficient method for extracting petroleum naphthas with a selective solvent such as sulphur dioxide.

A further object of our invention is to provide an extraction process whereby gaseous sulphur dioxide can be absorbed in the naphtha to be extracted.

A further object of our invention is to provide an extraction process whereby the used sulphur dioxide can be efficiently and cheaply recovered and re-used.

Further objects and advantages of our process will be apparent from the specifications when read in light of the drawing which gives a diagrammatic fiow plan of our process.

Petroleum naphthas obtained by cracking heavier oils contain large proportions of hydrocarbons and compounds which possess anti-detonating characteristics or anti-knock properties. Petroleum naphthas from other sources and processes such as the hydrogenation of hydrocarbon oils and polymerization of hydrocarbon oils may contain varying proportions of anti-detonating constituents which can be extracted by our process. Generally, the fractions of petroleum naphthas having an initial boiling point of about 240 F. and an end point oi 400 F. are preferable, but petroleum naphthas with somewhat lower or higher initial boiling points and lower or higher end boiling points may be used. For example,'

naphthas may be used which contain from 5 to of hydrocarbons boiling within the range of 160 to 200 F., and from S5 to 95% of hydrocarbons which boil below 390 F. to 435 F.; said naphthas may contain from to 50% of antidetonating constituents.

The quantitative amount of anti-detonating or anti-knock constituents in the naphtha and extract is expressed in octane numbers as determined by the CFR motor method described in ASTM method D357-33T.

By way of example and illustration we will describe the operation of our process when used to extract a cracked petroleum naphtha having an initial boiling point of about 250 F. and

an end boiling point of about 400 F. The naphtha to be extracted, or feed naphtha, is passed from the naphtha feed tank 10 by the pump II to the exchanger i2 wherein the naphtha is heated or cooled to the temperature employed in the step of dissolving gaseous sulphur dioxide in the naphtha. In this case a temperature of 80 F. was used. Any suitable heat exchanger medium such as water may be passed through the line I3 to effect the desired heating or cooling of the naphtha. The naphtha is then dried by a suitable means such as by passing it into the lower part of the tower I4 where it rises through a suitable drying agent such as sodium chloride, silica gel, calcium chloride, or the like. The dried naphtha is then passed by the conduit I5 to the upper part of the absorber l6 and permitted to descend through the absorber over the bubble plates ll, or equivalent means.

Dry S02 gas, which may be mixed with air and excess nitrogen, is passed by the conduit l8 through the exchanger I9 where it is cooled or heated to about 125 F. bv a suitable heating or cooling medium entering the exchanger through conduit 20. Generally, the temperature of the S02 gases entering the exchanger I9 is above 125 F., and water may be used to cool the gases to the desired temperature. In this particular example, the gaseous mixture entering line l8 contained about 90% oxygen and nitrogen and 10% $02. It was cooled with water from a high temperature to about 125 F. by the exchanger l9. The S02 gas may be obtained by burning sulphur or sulphur compounds as in the preparation of sulphuric acid. The S02 mixture is then passed by the blower 2! under a slight pressure of about 19 to 20 pounds per square inch absolute, through the conduit 22 to the lower part of the absorber i6 and there permitted to ascend through the absorber and be absorbed in the feed naphtha. If desired the pressure in the absorber I6 may be raised to 3 or 4 atmospheres absolute. A perforated pipe or an equivalent device may be used for introducing the gaseous sulphur dioxide into the bottom part of the absorber. After the sulphur dioxide has been used to extract the naphtha, a substantial portion thereof is recovered in the gaseous phase by the SOz-separators 5|, 53, 14,81, H3, and M0 and recycled by the manifold 58 to the absorber it; these SOz-separators and the recovery of the sulphur dioxide will be described later. The absorption of the S02 gas in the naphtha to be extracted tends to strip or force some of the low-boiling hydrocarbons or compounds out of the naphtha; so, in order to avoid this, a small amount of a naphtha which is somewhat heavier than the naphtha to be extracted is passed from the storage tank 23 by a pump 24 and conduit 25 to the top part of the absorber I 8. This heavier naphtha is introduced into the absorber i at a point above the point where the feed naphtha enters the absorber i8. This heavy naphtha re-absorbs these light hydrocarbons or constituents and prevents them from escaping through the vent 26. Also, this heavy naphtha tends to absorb any gaseous sulphur dioxide which was not absorbed in the naphtha. Generally, the temperature of the heavy absorbing naphtha is somewhat lower than the temperature of the naphtha being extracted, and consequently a cool zone of liquid is maintained in the upper part of the absorber HE. A cooler may be placed in the line 25 to accomplish this result. The vent stack 26 is provided on top of the absorber for removing the undissolved gases and air. An aspirator 260. may be placed in the vent stack to mix air with the vented gases, thereby rendering the admixture non-explosive.

The feed naphtha with dissolved sulphur dioxide is removed from the bottom part of the absorber l6 by the conduit 2'! and forced by the pump 28 through the heat exchangers 29 and 30 and cooled to about 5 F. The feed naph tha is then introduced into the extractor 3! by conduit 38a at a point intermediate the bottom and center of the extractor. Liquid sulphur dioxide is passed from the storage tank 32 by the pump 33 at a pressure of about 65 pounds per square inch absolute through conduit 35; to the heat exchanger or cooler 35, where it is cooled from atmospheric temperature to about 20 F., and thence into the upper part of chilling tower 36 where part of the liquid sulphur dioxide is flashed in order to cool the liquid sulphur dioxide to a temperature within the range of about 5 to +5 F. The pressure maintained in the chilling tower 36 may vary, but generally from 11 to 12 pounds per square inch absolute is satisfactory. The vaporized sulphur dioxide resulting from the flashing is recovered by a compression unit to be described hereinafter. A portion of the cold liquid sulphur dioxide is removed from the bottom part of the chilling tower 36 by the conduits 3i and 38 and passed through the exchanger 32 to aid in cooling the naphtha entering the extractor 3!; the S02 gas leaving the exchanger 35 is recovered by the compression unit described hereinafter. Cold liquid sulphur dioxide is withdrawn from the bottom of the chilling tower 36 through the conduits ST and 39 by the pump ii and forced into the top part of the extractor 3i. The cold liquid sulphur dioxide descends through the extractor 3! over the baffle plates and/or bubble plates or packing s2, and extracts the anti-detonating fraction of compounds and constituents from the ascending body of naphtha containing dissolved sulphur dioxide. The average temperature maintained throughout the extractor 3| is generally around 5 F.; however, higher or lower temperatures may be used, ranging from 10 F. to l25 F., although the preferred temperature ranges are 5 to -40 F. or from 30 to 7 0 F. The material which passes to the bottom or lowermost part of the extractor 3| comprises the suiphur dioxide extract or mixture of liquid sulphur dioxide and anti-detonating constituents. The material which rises to the top of the extractor 3| comprises the raffinate or extracted naphtha with some dissolved sulphur dioxide.

Recovery of sulphur dioxide from the S02- extract The SOz-extract is withdrawn from the bottom of the extractor Si by conduit 43 and forced by the pump 44 into the heat exchanger 35 where the temperature of the SOs-extract is raised from about 5 F. to about 60 to 70 F. The heated Soz-extract is then passed by the conduit 45 to the heat exchangers t6 and 47, where it is further heated to a temperature within the range of 70 to F. in the first exchanger and to F. in the second exchanger, and thence into the evaporator 58.

The sulphur dioxide is removed from the extract by a triple stage or multiple stage evaporator in which the temperature and pressure within each successive evaporator are progressive- 1y increased. By this type of evaporation, we effect considerable heat economy and operating cost, and recover a substantial portion of the sulphur dioxide in the liquid phase. The SO2- extract entering the evaporator is maintained at a temperature of about 97 F. and a pressure of about 73 pounds per square inch absolute.

The portion of sulphur dioxide that evaporates under the temperature and pressure maintained in evaporator 38 is removed from the top part of the evaporator by conduit 49 and passed to the condenser or heat exchanger 50, where it is cooled to a lower temperature of the order of about 90 to 92 and thence to the SOs-separator 3!, where the liquefied sulphur dioxide separates from the gaseous sulphur dioxide and constituents. The sulphur dioxide entering separator 5| is maintained at a temperature about 91 to 93 F. and at a pressure of about 72-74 pounds per square inch absolute. The liquid sulphur dioxide is passed from the bottom of the separator 5| through the cooler or heat exchanger 52, where it is further cooled to about 85 F. or atmospheric, temperature, and thence to the liquid-S02 manifold 53 where it is returned to the liquid-S02 storage tank 32 for further use in the extractor 3 l. Any suitable cooling medium may be used in the cooler 52. The permanent gases containing some gaseous sulphur dioxide which are collected in the top part of the separator 5| are passed by conduit 54 to the pressure reducing valve 55 and thence into the gaseous-S02 manifold 56. The S02 gas and permanent gases in manifold 58 are returned to the lower part of the absorber l6 and reabsorbed by fresh feed naphtha. By this step we are able to rc-use this portion of the gaseous sulphur dioxide in the extraction of naphtha without first liquefying the sulphur dioxide. The reducing valve 55 reduces the pressure of the S02 gases entering the manifold 56 to about the pressure of the gases entering the lower part of the absorber through conduit 22, that is, about 19 to 20 pounds per square inch ab solute; however, it should be understood that lower or higher pressures can be used.

The SOs-extract or bottoms in evaporator 48, from which some sulphur dioxide has been removed, is removed from the bottom thereof by the conduit 5". and forced by pump 58 under a higher pressure to the heat exchanger 59, where it is heated to a higher temperature, and thence to the second evaporator 68. The SOz-extract in the evaporator 38 should be maintained at a temoerature of about 124 F. and a. pressure of about 111 pounds per square inch absolute. The portion of sulphur dioxide which evaporates under the temperature and pressure maintained in the evaporator 60 passes through the conduit 6| to the heat exchanger 41, where it heats the fresh S02-extract entering the evaporator 48, and thence through conduit 62 to the SO2-separator 63 where the liquefied S02 separates from the gaseous S02. The materials in separator 63 are maintained at a temperature of about 116 F. and a pressure of about 111 pounds per square inch absolute. The liquefied sulphur dioxide is rethence to the manifold 53 moved from the bottom of the separator 63 and passed to the cooler or heat exchanger 64, where it is cooled to about 85 F. or atmospheric temperature, and thence to the liquefied-S02 manifold 53. The liquid sulphur dioxide entering the manifold 53 is returned to the storage tank 32 for further use in the extractor 3|. The permanent gases containing gaseous sulphur dioxide which collect in the top part of separator 63 are passed by conduit 65 to the pressure reducing valve 66 and thence into the S02-gas manifold 56 where they are returned to the lower part of the absorber l6 and reabsorbed by the fresh feed naph- ',tha. The reducing valve 66 reduces the pressure of the S02 gas entering the manifold 56 to about the pressure of the S02 gases entering the lower part of the absorber through the conduit 22; for example, about 19 to 20 pounds pressure per square inch absolute.

The S02-extract, from which some of the sulphur dioxide has been removed, is passed from the bottom of the second evaporator 66 by conduit 61 and forced by pump 68 under a higher pressure to the heat exchanger 69, where it is heated to a higher temperature by a suitable heat exchange medium entering conduit 16. Exhaust steam may be used as a suitable heat exchange medium for the heater 69. The extract is then passed to the evaporator H. The S02- extract in evaporator H is maintained at a tem perature of about 182 F. and a pressure of about 200 pounds per square inch absolute. The portion of sulphur dioxide which evaporates from evaporator H under the temperature and pressure prevailing therein passes through conduit 12 to the heat exchanger 59, where it heats the S02 extract passed from evaporator 48 to evaporator 60, and thence through conduit 13 to the S02-separator 14 where the liquefied sulphur dioxide separates from the uncondensed sulphur dioxide. The sulphur dioxide in separator 14 is maintained at a temperature of about 157 F. and a pressure of about 200 pounds per square inch absolute. The liquefied sulphur dioxide removed from the bottom of the separator 74 is passed through the heat exchanger 15 and cooled to about F. or atmospheric temperature, and where it is returned to the storage tank 32. The gaseous sulphur dioxide and gases which collect in the top part of the separator 74 are passed by conduit 16 to the pressure reducing valve 71 and thence into the SO2-gas manifold 56 where it is returned to the lower part of the absorber l6 and re-used to extract the fresh feed naphtha. The reducing valve 11 reduces the pressure of the S02 gas entering the manifold 56 to about the pressure of the S02 gas and air entering the lower part of the absorber through the conduit 22; for example, about 19 to 20 pounds per square inch absolute.

The S02-extract or unsaturated compounds remaining in evaporator H is withdrawn through the pressure reducing valve 78 and passed by the conduit I9 to the heat exchanger 80, where the S02-extract is heated. This heated extract is then passed through conduit 6| to the flash drum 82. The pressure reducing valve 18 releases the liquids into conduit 19 at a pressure of about 75 pounds per square inch absolute and this pressure is maintained within the flash drum 82.

The heat exchanger or heater 89 adds sufficient heat to the S02 extract or bottoms to practically compensate for the cooling effect caused by the flashing of the sulphur dioxide in drum 82. The temperature in the flash drum 82 is maintained at about 180 F. The flashed S02 gas passes through the conduit 83 to the heat exchanger 84, where it is cooled by a suitable heat exchange fluid, such as water entering the conduit 85, and thence through the conduit 86 to the S02-separator 87. The sulphur dioxide in separator 61 is maintained at a temperature of about 93 F. and a pressure of about 75 pounds per square inch absolute. The liquefied or condensed sulphur dioxide is removed from the bottom of the separator through the heat exchanger or cooler 83, where it is cooled to about F., or atmospheric temperature, and thence to the liquid-S02 manifold 53. The gaseous sulphur dioxide or uncondensed gases removed from the top of the separator 67 pass by conduit 89 to the pressure reducing valve 96 and thence into the S02-gas manifold 56 where it is returned to the absorber l6 and redissolved in the fresh feed naphtha. The pressure reducing valve 99 reduces the pressure of the S02 gas to about the pressure of the 0 S02 gases entering the lower part of the absorber [6.

The S02-extract which has had a substantial proportion of the sulphur dioxide removed, is passed from the flash through the pressure reducing valve 92, to the upper part of the extract stripper 93 and permitted to descend through said stripper over the baffle plates, bubble plates or packing material 94 disposed therein. The S02-extract near the bottom of the extract tower is trapped out by the tray 95 and passed by the conduit 96 through the heater 97, and returned to the stripper at a point below the trapout plate 95. The heater 9'! raises the temperature of the extract passed therethrough to a temperature of about 260 F. The pressure in the vapor space 98 or top part of the stripper should be maintained at about 7.5 to 8 pounds per square inch absolute. The stripped S02 gas and some extract vapors pass from the top of the stripper through conduit 99 to the condenser I00 where a substantial proportion of the vaporized extract is condensed and returned through conduit lol. This returned condensate or reflux is usually at a temperature of about 100 F. The uncondensed gases leaving the condenser 16!! are passed by conduit I02 to the gas compressor unit and liquefied; this gas compressor unit will be described hereinafter.

The extract or anti-detonating constituents which are now free from sulphur dioxide are removed from the bottom of the extract stripper 93 through the conduit M3 by the pump I04 and forced through conduit I65 and heat exchanger 46 to the extract storage tank I06. If desired, the extract may be washed with an alkaline solution to remove any trace of sulphur dioxide before the extract is blended with gasoline or motor fuel in order toraise the anti-knock value of said fuel. Also, the extract may be recombined with a part of the raflinate resultingv from the process, or the rafiinate may be cracked and then combined with the extract. If desired, the extract may be further treated before being blended with a motor fuel; for example, it may drum 82 by conduit 91 s be given a second extraction with S02 or other solvents.

In the above description of the recovery of sulphur dioxide from the SOz-extract, we have set forth specific temperatures and pressures for this process, but it should be understood that other temperatures, pressures and conditions may be used without departing from the scope of our invention. The particular temperature and pressure used will vary somewhat with the mode of operating the process and the nature of the naphtha extracted.

Sulphur dioxide recovery from the rafiinate The cold rafiinate removed from the top of the extractor 3! is passed by the conduit I! and the pump I08 through the heat exchangers 29 and I09, where it is heated to about 190 F., and thence to theflash drum H0. The rafiinate in the flash drum is maintained at a temperature of about 190 F. and a pressure of about '75 pounds per square inch absolute. The portion of sulphur dioxide evaporated in the drum H0 is passed through conduit I I I to the heat exchanger or condenser I I2, where it is cooled to about 93 F., and thence to the S02-separator H3. The sulphur dioxide in separator H3 is maintained at a temperature of about 93 F. and a pressure of about 75 pounds per square inch absolute. The condensed sulphur dioxide and gases removed from the bottom of the separator I I3 are passed to the exchanger or cooler I I4 and thence to the liquid- S02 manifold 53. Water or other suitable fluids may be used in the condenser H4 to cool the liquid sulphur dioxide to about atmospheric temperature. The uncondensed sulphur dioxide and gases in separator I I3 are removed from the top part thereof through conduit II5 to the pressure reducing valve H6 and thence to the S02-gas manifold 55 where they are returned to the absorber I6 and re-used. The pressure reducing valve II6 releases the gases into the manifold at about the pressure of the gases entering the lower part of the absorber I6.

The raflinate, containing some dissolved sulphur dioxide, is passed from the bottom of flash drum IIO by conduit II! to the pressure reducing valve II8, where the pressure is reduced to atmospheric pressure, and thence into the upper part of the rafiinate stripper II9, where the rafiinate is permitted to descend over the baffle plates, bubble plates, or packing material I20, disposed therein. Rafilnate in the lower part of the tower is removed from the trapout plate I2I by conduit I22 and passed through the heater or heat exchanger I23 where the raffinate is heated to about 260 F. Live steam or the like may be passed through conduit I24 as a heating medium. The heated raffinate is returned by conduit I25 to the bottom part of the stripper where it materially aids in removing the dissolved sulphur dioxide from the raffinate. The stripped or vaporized sulphur dioxide with a small amount of rafiinate vapors, are removed from the top of the raifinate stripper II9 through conduit I26 to the condenser I21 Where the rafilnate vapors are condensed and returned by the conduit I28 to the top part of the raffinate stripper. The condensed materials returning to conduit I28 are usually at a temperature of 120 F. and pressure maintained in the upper part of the rafiinate stripper H9 is about 7 to 8 lbs. per sq. in. absolute. Any suitable cooling fluid, such as water, may be passed through conduit I 36 to produce the desired cooling efiect in the condenser I27. The

uncondensed materials and S02 gas pass from the condenser I 21 by the conduit I3I to the manifold I02 and returned to a compressor unit which will be described hereinafter.

The stripped railinate is passed from the bottom of the stripper H9 by the conduit I32 to the pump I33 and forced through conduit I34 and heat exchanger I09 to the washer I35 where the raffinate is washed with an alkaline reagent such as an aqueous sodium hydroxide solution to remove the last traces of sulphur dioxide. Any convenient tower or washing means may be used to remove the last traces of sulphur dioxide from the raffinate. The washed rafiinate is then passed by conduit I36 to the rafiinate storage tank I 37. This raifinate may be recracked at high temperature and the product again extracted by passing it to the bottom of the absorber I6.

The S02 gas, containing some hydrocarbon materials and compounds, removed from the extract stripper 93 and railinate stripper H9, is passed through conduit I02 to the gas booster I38 where it is forced through the conduit I39 to the separator drum I40. The pressure in conduit I 02 is usually about '7 to 8 pounds per square inch. The flashed S02 gas from the chiller 36 is also passed to the separator drum I40 by the conduit MI. The pressure maintained in the separator drum I40 is the same as the pressure maintained in the top part of the chiller 36; that is, about 11 to 12 pounds per square inch absolute. The entrained liquids and condensed naphthas settle to the bottom of the separator drum I40 and are withdrawn through the valved conduit I42. The

S02 gas passes from the top of the separator drum I40 through conduit I43 to the bottom part of the drier I 44. Solid drying agents such as calcium chloride or sodium sulphate may be used to dry the S02 gases, similarly, strong sulphuric acid may be passed countercurrently to the stream of S02 gases in order to dry the same. The dry S02 gas is passed by the conduit I45 to the compressor I46 where it is compressed to a pressure of about '70 pounds per square inch absolute. The compressed gases are then cooled by the condenser I41 and passed to the S02 separator I48. The liquid sulphur dioxide is passed from the bottom of the separator I48 by conduit I49 and returned to the liquid-S02 manifold 53. The uncondensed gas passes from the top of the separator I48 through the pressure reducing valve I50 where the pressure is reduced to about 19 to 20 lbs. per sq. inch absolute, and thence through the conduit 56 to the bottom part of the absorber I6.

In the operation of our extraction process it will be observed that the sulphur dioxide is recovered from the extract and rafiinate by three difierent methods. In the SOz-separators 5|, 63, I4, 81, H3, and I48, the gaseous sulphur dioxide is recycled by the S02-gas manifold 56 to the bottom of the absorber I6 and reabsorbed in the hydrocarbon naphtha to be extracted and consequently recompression of the S02 gases before reusing the same is avoided. The liquid S02 recovered in the above six S02 separators is returned to the liquid-S02 storage tank 32 and then returned to the extractor 3I (after passing through chilling tower 36) where it is used in the extraction of the naphtha. The gaseous sulphur dioxide recovered from the extract stripper 93, rafiinate stripper II9, chilling tower 36 and heat exchanger 30 are compressed by the compressor I46, liquefied and returned to the storage tank 32 and then reused in the extractor 3i. herein described process a substantial portion of By our the S02 used to extract the naphtha is recovered and reused to extract fresh naphtha without being recompressed or recondensed. After our process has once made a complete cycle of operation, the lost sulphur dioxide is replaced by the S02 gases from the sulphur burners or acid plant which enter the conduit i8.

It should be understood that the temperatures, pressures, and conditions of operation will vary somewhat with the manner and mode of operating the plant and that the use of different temperatures, pressures, etc. do not depart from the scope of our invention. The particular characteristics of the naphtha to be extracted will somewhat determine the pressure and temperature conditions to be used.

In the SOz-separators 51, 63, M, 81, H3, and M8, the conventional type of float valve may be disposed therein to maintain a predetermined amount of liquid sulphur dioxide in the separators. Generally the liquid level in these separators is from to /2 full.

The amount of sulphur dioxide used in our process may vary with the type of naphtha extracted, temperatures used and other operating conditions. As one example or" our process, 370 barrels of cracked naphtha of 50 A. P. I. may be put through the process in one hour and 1'78 barrels of extract and 192 barrels of raffinate obtained. In this example, about 560 pounds of S02 gas are absorbed in the absorber l6 and 373,000 pounds of liquid sulphur dioxide are used in the extractor 3|. Also, about 96% of the sulphur dioxide used is recovered in the liquid phase, without any recompressing, from the separators 5|, 53, 14, 81, H3, and M3; about 0.05% of the sulphur dioxide is recovered as a gas and reabsorbed in the absorber l6; and about 4% of the sulphur dioxide (exclusive of that used in exchanger 3?! to cool the naphtha and of that evaporated to take care of heat losses) is recovered as a gas and liquefied by the compressor unit. Not more than 0.1% of the sulphur dioxide entering the system is lost.

While we have described our process with reference to specific temperatures, pressures, volumes and operating conditions, it should be understood that our invention is not restricted by such limitations. The above conditions of operation may be altered by those skilled in the art without departing from the scope of the invention as set forth in the claims and specification.

We claim:

1. In the continuous process of separating petroleum naphtha containing detonating and antidetonating constituents into fractions respectively which are more detonating and more antidetonating than the original naphtha, the steps comprising dissolving gaseous sulphur dioxide in said naphtha by countercurrently contacting said naphtha with gaseous sulphur dioxide, cooling said naphtha solution, extracting said naphtha solution with liquid sulphur dioxide, separating most of the sulphur dioxide from the sulphur clioxide extract by multiple-stage evaporation wherein the temperature and pressure in each successive stage are progressively increased, cooling the vaporized sulphur dioxide to effect condensation of a part thereof, separating the condensed sulphur dioxide from the uncondensed sulphur dioxide and recycling both the condensed and uncondensed sulphur dioxide to aid in the further extraction of the petroleum naphtha.

2. In theprocess of separating petroleum naphthas containing detonating and anti-detonating constituents into fractions respectively which are more detonating and more anti-detonating than the original naphthas, the steps comprising simultaneously extracting a heavy naphtha and a lighter naphtha, continuously passing the light naphtha coiuitercurrent to and in contact with gaseous sulphur dioxide and nitrogen in a vertical elongated contact zone, continuously adding a small amount of the heavier naphtha near the top part of said contact zone to recover vapors of the light naphtha, continuously removing the combined naphtha solution of sulphur dioxide from the lower part of the contact zone, passing the said solution countercurrent to and in contact with liquid sulphur dioxide in a second contact zone, and separating the sulphur dioxide extract from the remainder of the naphtha solution.

3. In the process of separating petroleum naphtha containing detonating and anti-detonating constituents into fractions respectively which are more detonating and more anti-detonating than the original naphtha, the steps comprising continuously passing the naphtha countercurrent t0 and in contact with gaseous sulphur dioxide in a vertical elongated contact zone, adding a small amount of a heavier naphtha near the top part of said contact zone, removing the naphtha solution of sulphur dioxide from the lower part of the contact zone, cooling said naphtha solution of sulphur dioxide to a temperature within the range of 5 to -10 F., passing said cold naphtha solution of sulphur dioxide countercurrent to and in con tact with liquid sulphur dioxide at a temperature within the range of 5 to -10 F. in a second con tact zone, separating the sulphur dioxide-extract from the remainder of the naphtha solution, and then separating substantially all of the sulphur dioxide from the extract by multiple-stage evaporation wherein the temperature and pressure in each successive stage are progressively increased.

i. In the process of separating petroleum naphthas containing detonating and anti-detonating constituents into fractions respectively which are more detonating and more anti-detonating than the original naphthas, the steps comprising simul taneously extracting a heavy naphtha and a lighter naphtha, continuously passing the light naphtha countercurrent to and in contact with a mixture of gases containing sulphur dioxide and nitrogen in a vertical elongated contact zone, adding a small amount of the heavier naphtha near the top part of said elongated contact zone to recover vapors of the lighter naphtha, continuously removing the naphtha combined solution of sulphur dioxide from the lower part of the contact zone, cooling said naphtha solution, passing said naphtha solution countercurrent to and in contact with liquid sulphur dioxide at a temperature within the range of 10 to 60 F. in a second contact zone, and separating the sulphur dioxide extract from the remainder of the naphtha solution.

5. In the process of separating petroleum naphtha containing detonating and anti-detonating constituents into fractions respectively which are more detonating and more anti-detonating than the original naphtha, the steps comprising dissolving gaseous sulphur dioxide in said naphtha by countercurrently contacting said naphtha with gaseous sulphudioxide, cooling said naphtha solution, extracting said naphtha solution with liquid sulphur dioxide at a temperature within the range of 5 to 10 F., separating most of the sulphur dioxide from the sulphur dioxide-extract by multiple-stage evaporation wherein the temperature and pressure in each successive stage are progressively increased, and then separating the remainder of the sulphur dioxide from the extract by flashing and heating the same.

6. In the continuous process of separating petroleum naphtha containing detonating and antidetonating constituents into fractions respectively which are more detonating and more anti-detonating than the original naphtha, the steps comprising passing the naphtha countercurrent to and in contact with gaseous sulphur dioxide in a vertical elongated contact zone, adding a small amount of heavier naphtha near the top part of said elongated contact zone, continuously removing the naphtha solution of sulphur dioxide from the lower part of the contact zone, cooling said naphtha solution, passing said naphtha solution countercurrent to and in contact with liquid sulphur dioxide at a temperature within the range of 10 to 60 F. in a second contact zone, separating the SOz-extract from the remainder of the naphtha solution, separating most of the sulphur dioxide from the SOz-extract by multiple-stage evaporation wherein the temperature and pressure in each successive stage are progressively increased, cooling the vaporized sulphur dioxide to efiect condensation of a part of the same, separating the liquid sulphur dioxide from the sulphur dioxide vapors, recycling the sulphur dioxide vapors to the vertical elongated contact zone, and recycling the liquid sulphur dioxide to the second contact zone.

7. In the continuous process of separating petoleum naphtha containing detonating and antidetonating constituents into fractions respectively which are more detonating and more anti-detonating than the original naphtha, the steps comprising passing the naphtha countercurrent to and in contact with gaseous sulphur dioxide in a vertical elongated contact zone, adding a small amount of heavier naphtha near the top part of said elongated contact zone, continuously removing the naphtha solution of sulphur dioxide from the lower part of the contact zone, cooling said naphtha solution, passing said naphtha solution countercurrent to and in contact with liquid sulphur dioxide at a temperature within the range of 10 to 60 F. in a second contact zone, separating the SO2-extract from the remainder of the naphtha solution, separating most of the sulphur dioxide from the sulphur dioxide-extract by multiple-stage evaporation wherein the temperature and pressure in each successive stage are progressively increased, 'cooling the vaporized sulphur dioxide to effect condensation of a part of the same, said cooling being accomplished at least in part by indirect heat exchange between the vaporized sulphur dioxide from one stage and the liquid material passing to the next preceding stage, separating the liquid sulphur dioxide from the sulphur dioxide vapors, recycling the sulphur dioxide vapors to the vertical elongated contact zone, and recycling the liquid sulphur dioxide to the second contact zone.

ERNEST W. THIELE. FRED W. SCHEINEMAN. 

